HD aggregation & packet services accelerate video switch/router bandwidth

Video switching has encountered two technology trends that together are changing tasks in the professional studio radically. Native signals used in video editing evolved from analog to SD(standard definition) digital, then quickly to HD (high definition) and several higher-ban ***a***dwidth standards.

At the same time, video aggregation that once was characterized by point-to-point dedicated digital streams is poised to take advantage of packet-switching technologies, with Ethernet showing particular promise as a Layer 2 delivery mechanism.

Of course, video switching, as defined by the professional studio, is quite different from the packet switching technology used in the enterprise LAN, or even the WAN backbone. At the same time, modifications and extensions to core technology have resulted in carrier Ethernet technologies that are enabling a migration of Ethernet from the enterprise to carrier networks.

The advantage in Ethernet adoption has been a uniform standard resulting in higher volumes, thereby driving down deployment and operating costs. In addition, the emergence of 10Gbps Ethernet bandwidth per link and audio/video specific mechanisms, such as audio/video bridging (AVB), lay the groundwork for delivery, transport and switching of uncompressed HD content in studio environments.

Before HD signals became prevalent, professional studio mixers and switchers manipulated SD and composite video signals, hardware needs were significant but did not always define the state-of-the-art highest performance driven by routers in communications markets.

The slow but steady arrival of 3G HDTV, 3D HDTV, 4K2K, and Super Hi-Vision (Ultra HD) brings bandwidth requirement speeds to the tens of gigabits per second. This speed demand will be accelerated further by expansion of local, national and international HD productions and the anticipated move to 1080p and 3D broadcasts which will drive up storage and intra-box communications links in a studio environment.

Meanwhile, the effort to move the first stage of editing and mixing video content from centralized studios to remote digital TV vans has placed new demands on hardware to reach new milestones in low power and high integration. These two goals now exceed the demands for signal quality that will maintain uninterrupted broadcasts to the viewing audience(Figure 1 below).

Changes in site-based video switching have followed two related trends favoring denser switches. The arrival of IP gateways in video networks has made it possible in some network topologies for broadcasters to capture and transmit uncompressed HD video from remote sites.

Also, broadcasters seek to simplify overall transmission-system architectures through the use of denser, higher-performance switches that carry the potential of replacing bulky remote studio trailers that are often the size of semi trucks. Miniaturized video switching platforms could lead to reduced sizes, lower power and simplified architectures in remote transmission.

HD aggregation & packet services accelerate video switch/router bandwidth

Figure 1: New technologies are enabling new architectural alternatives for the traditional video router function.

An emerging trend is the packetization of high-bandwidth traffic, a familiar trend that has played out in telecommunications and carrier environments. Digital video editing highlights some of the architectural demands of new video switching architectures. The video industry has evolved from analog input and composite traffic over RF cable, to emerging architectures featuring sophisticated control, scalability and embedded audio capabilities.

This is similar to some of the operations, management and performance monitoring functions enabled in carrier Ethernet technologies. While video switches still push performance and scalability on a larger scale than multiport Gigabit Ethernet switches, the chip-level requirements are sharing more in common with packet switches, particularly in integrated low latency routing and Quality of Service packet prioritization methods. In addition, precision timing protocols such the IEEE 1588 protocol allows packet synchronization and precision timing in the sub-microsecond range.